Positively driven spiral systems, in which drive structure on the outside of a rotating cage engages structure on the inside of a conveyor belt, have been used to convey articles, such as foodstuffs and other materials, through cooled or heated environments. Spiral conveyors, in which a conveyor belt follows a helical path winding around a central tower, drum, or cage, are used in freezers, coolers, proofers and ovens to provide a long conveying path with a small footprint. Cage-bars extending from the top of the central cage to the bottom are spaced apart circumferentially and form the outside of the cage.
As disclosed in U.S. Pat. No. 8,181,771 (Talsma), metal cage-bars form a drive structure that drives the belt. Because there is positive engagement between the regularly spaced drive structure on the cage and regularly spaced edge structure on the inside edge of the belt, there is no slip as in overdrive spiral systems. No additional tensioning is needed and frictional losses are less.
However, prior art positively driven spiral systems have difficulties in cleanly engaging the belt and disengaging it from the drive structure on the cage. To help solve that problem, the cage-bars have a ridge of varying height at the entrance of the conveyor belt into the rotating cage.
There is however a need to provide an improved cage-bar that has the objective to convey a smooth surface, the smooth surface aiming at providing a more sanitary device. It is also a need to provide a more flexible cage-bar with regards with the conical shape of the central cage (?) and less wear-prone. Another objective of the present invention is to propose an improved cage-bar that would be less expensive to manufacture.